Particle drift potential of glyphosate plus 2,4 D choline pre-mixture formulation in a low-speed wind tunnel

Authors: VIERA, BRUNO - University Of Nebraska; BUTTS, THOMAS - University Of Nebraska; RODRIGUES, ANDRE - University Of Nebraska; SCHLEIER, JEROME - Corteva Agriscience; Fritz, Bradley - Brad; KRUGER, GREG - University Of Nebraska

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2020
Publication Date: 2/3/2020
Citation: Viera, B., Butts, T., Rodrigues, A., Schleier, J., Fritz, B.K., Kruger, G. 2020. Particle drift potential of glyphosate plus 2,4 D choline pre-mixture formulation in a low-speed wind tunnel. Weed Technology. https://doi.org/10.1017/wet.2020.15.
DOI: https://doi.org/10.1017/wet.2020.15

Interpretive Summary: While the introduction of 2,4-D-tolerant crops provides growers a new post-emergent weed management product, the technology raises concerns with respect to off-target movement and damage of sensitive vegetation and the need to consider spray nozzles and operational settings that improve droplet size. Wind tunnel evaluations using two nozzle types, each producing a different droplet size, showed that both the droplet size and the speed at which the droplets exited the nozzle played a significant role in the measured drift potential and biological impact to soybean plants, and should be considered when making any spray application. This work provides guidance to applicators and researchers on the proper use and setup of spray systems when applying 2,4-D in areas surrounded by sensitive species.

Technical Abstract: The introduction of 2,4-D-tolerant crops provided growers a new postemergent active ingredient to include into weed management programs. The technology raises concerns regarding potential 2,4-D off-target movement to sensitive vegetation, and spray droplet size is the primary management factor focused on to reduce spray particle drift. Droplet velocity is another component often overlooked that influences spray drift potential, in which droplets with higher vertical velocities have less drift potential. Venturi nozzles are widely used for 2,4-D applications because they increase the spray droplet size and reduce spray drift potential. They tend to produce slower droplets because of the pressure drop caused by air-inclusion and preorifice components. The objective of this study was to investigate the droplet size distribution, droplet velocity, and particle drift potential of glyphosate plus 2,4-D pre-mixture (Enlist Duo ®) applications with two commonly used venturi nozzles in a low-speed wind tunnel. Applications with the TDXL11004 nozzle had larger D V0.1 (291 µm), D V0.5 (544 µm), and D V0.9 (825 µm) values compared to the AIXR11004 nozzle (250, 464, and 709 µm, respectively), and slower average droplet velocity (8.1 m s -1 ) compared to the AIXR11004 nozzle (9.1 m s -1 ). Nozzle type had no influence on drift deposition (P = 0.65), drift coverage (P = 0.84), and soybean biomass reduction (P = 0.76). Although the TDXL11004 nozzle had larger spray droplet size, the slower spray droplet velocity could have influenced the nozzle particle drift potential. As a result, both TDXL11004 and AIXR11004 nozzles had similar spray drift potential. Further studies are necessary to understand the impact of droplet velocity on drift potential at field scale, and test how different tank solutions, sprayer configurations, and environmental conditions could influence the droplet size and velocity dynamics and consequent drift potential in pesticide applications.